High-pressure lubricant



United States Patent 3,382,173 HIGH-PRESSURE LUBRICANT Hermann Zorn and Erwin Steininger, both Technochemie G.n1.b.H., Heiligenbergstn, 1b, Heidelberg, Germany No Drawing. Continuation-impart of application Ser. No. 148,014, Oct. 23, 1961. This application June 15, 1964, Ser. No. 375,977 Claims priority, application Germany, Dec. 23, 1960, T 19,459 5 Claims. (Cl. 25249.8)

This invention relates to high pressure lubricants, and more particularly to organic phosphorus compounds which are useful lubricants even under conditions of high temperature and high pressure, and which improve the performance of conventional lubricants when admixed thereto in relatively minor amounts.

This application is 'a continuation-in-part of our copendin-g application Ser. No. 148,014, filed on Oct. 23, 1961, now abandoned, in which We disclosed methods for producing certain biphosphines of the formula wherein R and R may be aryl, alkyl, or aralkyl radicals, R moreover may be hydrogen, and n is an integer not smaller than 6, and preferably ten or greater. If the carbon chain connecting the phosphorus atoms is branched, it should have a straight length of at least six carbon atoms.

The bis-phosphines of the invention are more or less viscous liquids whose viscosity changes relatively little with temperature, and which resist heating to elevated temperature for extended periods. The thermal stability of the bi-phosphines of the invention increase with increasing length of the carbon chain connecting the phosphorus atoms, and the thermal changes in viscosity also decrease with increasing carbon chain length.

The viscosity change at high temperatures is further reduced if at least one of R and R is an 'alkyl radical having a long carbon chain, and even better results are obtained when substituted aromatic radicals constitute R or R. Alkyl substituted aromatic radicals particularly enhance the valuable lubricant properties of the bi-phosphines.

The thermal resistance of the bi-phosphines of the invention also makes them suitable as hydraulic fluids under severe conditions of use. Those bi-phosphines of the invention which have aromatic radicals attached to the phosphorus atoms have mild reducing properties, and thus protect other ingredients of a lubricant composition against oxidation.

Several methods are available for synthesizing the biphosphines of the invention. According to a preferred method, two molecules of a secondary phosphine are condensed with a dihalogenated hydrocarbon molecule. Primary or secondary, bis-primary or bis-secondary phosphines are reacted to replace all free hydrogen atoms on the phosphorus atom by alkali metal. Lithium is the preferred alkali metal, and butyllithium the preferred reagent for introducing the lithium atom. The alkali metal phosphine compound may then be further reacted with alkyl monoor dihalides. The phosphine starting material may also be brominated to the corresponding monobromophosphine which may be further reacted with Grignards reagent or with other organometallic compounds.

The manner in which the biphosphines of the invention may be prepared is further illustrated by the following examples, and those skilled in the art will readily apply these teachings to homologous and analogous bi-phosphines of the invention.

EXAMPLE 1 A mixture of 387 parts by volume dodecyl butyl phosphine (c zHgs-pH-cqllg) with 400 parts of tetrahydrofurane was prepared under a nitrogen atmosphere in a flask equipped with a reflux condenser. While the contents of the flasks were kept at a temperature between 20 and 50 degrees Centigrade, a 3.5 molar solution of butyllithium in hexane was added to the phosphine solution drop by drop until the added butyl lithium amounted to 390 parts by volume.

When these reactants had been combined, the solution was refluxed for three hours, and 161 parts 1.8-dibromooctane were then added drop by drop. Water was there after added to the reaction mixture until it separated into two layers. The non-aqueous phase was dried by means of anhydrous sodium sulfate. The solvents were evaporated, and the excess of unreacted phosphine was distilled off by heating at a pressure of 0.1 mm. Hg to 220 C.

318 parts octamethylene bis-dodecyl-butyl-phosphine were obtained. The product has a boiling point of 230 C. at 0.001 mm. Hg, and may be purified by distillation. The refractive index 12 is 1.4843, the specific gravity at 20=0.8670.

EXAMPLE 2 A solution of 208 parts tolylhexylphosphine in 1500 parts anhydrous ethyl ether was refluxed for 12 hours with 23 parts sodium wire in 'a nitrogen atmosphere. When the sodium has been completely consumed, a solution of 191 parts dibromononadecane in 250 parts ether was added. The reaction mixture was refluxed for one hour, and worked up by addition of water and fractionation of the organic solvent phase in the manner described in Example 1.

262 parts nonadecylene-bis-tolylhexylphosphine were obtained, and may be purified by vacuum distillation. lZ =1.5181, sp. gr. =().l93().

EXAMPLE 3 35.2 parts potassium were dispersed in 200 parts octane in a flask equipped with a reflux condenser in a nitrogen atmosphere. A solution of 185 parts diphenyl phosphine in 500 parts octane was added drop by drop, while the temperature of the resulting mixture was held between 60 and C. The completed mixture was heated for another hour to 80-100 C., and then cooled to a temperature between 60 and 80 C. At that temperature, a solution of parts dichlorononadecane in 200 parts octane was added. The reaction was completed by refluxing for two hours, and the reaction mixture was decomposed by addition of 300 parts water, drying of the organic solvent phase, and distillation in the manner described in Example 1.

142 parts nonadecylene-bis-diphenylphosphine were obtained as a highest boiling residue. n =l.5794, sp. gr. =().9748.

EXAMPLE 4 20.2 parts sodium wire were immersed in 200 parts ether in a nitrogen atmosphere. A solution of 108 parts primary tolyl phosphine in parts dry ethyl ether was added, and the mixture was refluxed for two hours. 128 parts dibromononadecane were gradually added thereafter, and the reaction mixture so obtained was refluxed for two hours.

200 parts of water were added, and the organic solvent phase was worked up as described in Example 1. 132

parts non adecylene-bis-monotolylphosphine were obtained. n =l.5368, sp. gr. =0.949l.

EXAMPLE 5 19.5 parts potassium were suspended in 300 parts hexane, and 124 parts decamethylene-bis-phosphine were The lubricating properties of representative biphosphines of the invention and of chemically related compounds are shown in the following tables. In these tables, the substances tested are identified by code letters as follows:

added While the mixture was being kept at a temperihosphine ature between and C. The mixture was refluxed lenebisbug do dec p p for one hour, and 83 parts l-bromohexane dissolved octglene bis butgbdodecawhosphine m parts hexane-wen addgd' 0 E. Decylene bis-butyl-dodecyl phosphine The reaction mixture was further processed as de- F Nonadecylene bis but do decyl hosphine scribed in the preceding examples, and parts deca- Dec lamb; henylgexyl hos phine methylene-bis-monohexylphosphine were obtained. The g f p g p g compound boils between and C. at 0.05 mm.

H g nD20=L 4631 Sp. grmzogzm 15 I. Nonadecylene bis tolyl hexyl phosphine EXAMPLE 6 The procedure of Example 1 was repeated using a solution of 102 parts nonadecylene-bis-monotolylphosphine in dry tetrahydrofurane, butyllithium, and 66 parts l-bromohexane as the reactant. 9l parts nonadecylenebis-tolylhexylphosphine were obtained. n =l.5181, sp. gr. =O.9130.

I. Nonadecylene bis-tolyl-isobutyl-phosphine The viscosity of each substance in centistokes at 100 F. was determined initially, after six hours heating at 280 'C. in a nitrogen atmosphere, after further heat treatment in a nitrogen atmosphere at 290 C., and so forth, until cumulative heat treatment was discontinued because of major changes, or until at last heat treatment had been applied at 350 C.

TABLE 1 Last Heat Viscosity, Centistekes at 100 F Treatment at C A B C D E F G H I J l Crystalline precipitate.

2 Highly viscous, but transparent.

Viscosity not measurable, solid precipitate. Norm-The viscosity values after heat treatment tabulated in Table 1 are again listed in Table 2 as percentage changes in the original viscosity.

TAB LE 2 Last Heat Viscosity Change, Percent Treatment,

EXAMPLE 7 A solution was prepared from 100 parts nonadecylenebis-monohexylphosphine and 200 parts chloroform. While a temperature between 0 and 10 C. was maintained, a mixture of 64 parts bromine and 150 parts chloroform was added. The solvent was distilled off. The brominated product was dissolved in 200 parts ether, and the solution was added drop by drop to a solution of 0.4 equivalents phenylrnagnesium bromide in 200 parts It is evident from Tables 1 and 2 that compounds G to I which have aromatic nuclei directly attached to phosphorus atoms separated by long alkylene chains are superior to compounds A to F in their high temperature stability. The appearance of compounds G to J was further graded qualitatively after the several successive heat treatments. The following evaluation code applies to Table 3:

1 Colorless (a) Clear ethyl ether. The mixture was refluxed for one hour. Upon 2 y ll i Slight precipitate addition of 200 parts saturated aqueous ammonium chlo- G0 3 Y ll p i i ride solution, an organic solvent phase was formed. It 4 Li h brown was dried, and the solvent was evaporated. 63 parts 5 D brown nonadecylene bis-phenylhexylphosphine were obtained. The product boils at 250 C. under a pressure of 0.001 TABLE 3 mm. Hg n =1.5225, sp. gr. =0.9270. (35 l' g gggg Compound o H 1 J EXAMPLE 8 (a) 1 (a) 1 (a) 1 (a) 100 parts nonadecylene-bis-monohexylphosphine were (a) i8; brominated as in Example 7, and the bromination prodg; not was reacted with butyllithium. The reaction prod- 3 5(a) 3(1)) not was treated with water and worked up as described 350 :2?

in the preceding examples. 53 parts nonadecylene-bishexylbutylphosphine were obtained. n =1.4852, sp. gr. =0.8678.

The difference in viscosity at different temperatures can be controlled in the bisphosphines of the invention by the selection of suitable radicals R and R as will be evident from the following Table Aliphatic radicals having a long, straightchain improve the viscosity index and reduce the pour point.

6 ly and restricted solely by the scope of the appended claims.

What we claim is: 1. A method of lubricating metal surfaces arranged TABLE 4 Pour Compound C. 100F 50C. 210 F. V.I. V.P. m paint,

The bi hospines of the invention are useful lubricants, for movement relative to each other which comprises inp a e 6 when used singly or in mixtures with each other, but they terposing between sa1d surfaces a film of a lubricant cornare particularly useful additives for conventional lubricat- 20 position including at least one percent of a liquid organic ing oils. They significantly improve the resistance of the bi-phosphine of the formula lubricating film to high contact pressure and reduce the tendency to sludge formation. The following examples R1 illustrate typical improvements obtained in conventional P-(CHzh-P lubricating oils by admixture of a bi-phosphine of the R2 R2 invention.

EXAMPLE 9 wherein R and R are members of the group consisting 95 parts of a commercial automotive lubricating oil of alkyl, and aryl rad1cals, and wherein n is an integer of viscosity SAE 20 and mainly consisting of petroleum g i t f th l 1 h hydrocarbons were mixed with 5 parts nonadecylene-bisme o Se f m alm w.erem Sal tolyusobutyLphosphinei A clear solution was obtained. 1ubr1cant compos1t1on cons1sts mamly of a ma or amount Samples of the mixture and of the unmixed commercial i i hyfkogrbons of a mmor amount of product were subjected to tests for film strength on an ig ,g g f fh 1 h d1 b extremeapressure lubricant testing machine of the wellme as e w .erem Sal u known Almen type as modified by Wieland. Seizing oc- Clint composmon y nialor am9unt 0f current at 1,000 when the mixture of SAE 20 oil with dlester i of sald i f organic the phosphine was employed as a lubricant between bear- A lubricant composmon mamly conslstmg ing and shaft. 'In the absence of the phosphine the commajor amount. petro1el1m.hydroc?rbns and a mmor mercial Product prevented seizing y up to 3:00. amount of a l1qu1d organic blphosphlne of the formula EXAMPLE 10 40 R1 1 A synthetic diester oil having a viscosity of 4.5 cen- B40759? tistokes at 210 F. was mixed with nonadecylene-bis- R1 R5 tolyl-isobutyl-phosphine in a ratio of 95:5. The clear homogeneous liquid obtained was tested on the afore- Wnarem R1 and R2 members of E coflslstmg mentioned Almemwieland testing apparatus in compari of alkyl, and aryl radicals, and Wherem n 18 an mteger son with the unmixed diester oil. The admixture of the and at least phosphine improved the seizing load from 900 to 1150. A lubncant 891119051999 mamly Qonslstmg of a Admixtures of bi phosphine as low as one percent Sig ma or amount of a diester 011, and of a minor amount of nificantly improve the strength of conventional lubricant a liquid Organ: blphosphme of the formula films under extreme pressure, and even lower concentra- R R1 tions produce measurable improvement. An increase in the phosphine concentration of a mixed lubricant beyond P"(CH)HP 5 percent does not normally result in better performance R4 R, as long as the conventional component of the lubricant 0 mixture prevails whereln R and R are members of the group consisting It is not fully understood why admixed bi phosphines of alkyl, and aryl radicals, and whereln 12 18 an mteger and improve the pressure resistance of lubricant films interat least posed between bearing metal surfaces which move rela- R f d tive to each other under high pressure. It is believed that e erences e the biphosphines are selectively adsorbed on the bearing UNITED STATES PATENTS surfaces, and that a film of high strength and low fric- 2612474 9/1952 Morgan et a1 t1on coefiic1ent 1s thereby formed. The hlgh temperatures 3,086,055 4 /1963 Wagner 5 5 generated m a bearlng under heavy load are belleved to 3 113 951 1 19 4 Burg et 1 2 0 5 favor adsorpt1on of the phosphine. 60 3,160,593 12/1964 spooncer The phosphines are effective not only in lubricating bearings, as in the Almen machine test, but also for gear lubrication and, for the lubrication of pistons in internal combustion engines, and the like.

While the invention has been described with particular reference to specific embodiments, it is to be understood that it is not limited thereto, but is to be construed broad- DANIEL E. WYMAN, Primary Examiner.

LEON D. ROSDOL, CARL D. QUARFORTH, REU- BEN EPSTEIN, Examiners.

W. H. CANNON, L. A. SEBASTIAN,

Assistant Examinjers. 

4. A LUBRICANT COMPOSITION MAINLY CONSISTING OF A MAJOR AMOUNT OF PETROLEUM HYDROCARBONS, AND A MINOR AMOUNT OF A LIQUID ORGANIC BIPHOSPHINE OF THE FORMULA 